Imagine that it is a clear autumn day-just the right kind of day for a trip down the coust ! One way to visit our coust is to follow an old trail that is now Highway 101.In chapter 1 you read about the Colombia River ,wich forms most of the northern border of our state.Lets start our trp at the river's moth , where the Colombia meets the pacific Ocean.The mouth of a river is a place where the river empties into a large body of water.